Lubrication system for limited slip differential

ABSTRACT

Limited slip differential which is selectively engageable and includes an improved lubrication system. The limited slip mechanism uses a spring loaded friction disk clutch pack which can break away at excessive torque levels and prevent axle shaft breakage. The novel lubrication system provides improved lubrication of the clutch pack under all operating conditions and prolongs the life of the clutch pack.

United States Patent 11 1 Wilder ct a1.

14 1 Oct. 2, 1973 I LUBRICATION SYSTEM FOR LIMITED SLIP DIFFERENTIAL[75] Inventors: William H. Wilder, Lynd hurst; lvan E. Benjamin, EastCleveland, both of Ohio [73] Assignee: Eaton Yale & Towne Inc.,Cleveland,

Ohio

[22] Filed: Apr. 14, 1971 21 Appl. No.: 134,065

Related US. Application Data [63] Continuation of Ser. No. 841,088, July11, 1969,

abandoned.

52 u.s.c1. ..l84/6.12,74/7ll,-l92/113B 51 1111.01 ..Fl6h 1/44 [58] FieldofSearch ..192/ll3.2;l84/6,

[56] References Cited UNITED STATES PATENTS Nelson 184/612 X 3,198,2958/1965 Fungman et 211,... 192/113 B 3,153,464 10/1964 Nelson ct al 184/6X 3,202,253 8/1965 Merritt et a1... 192/113 B 3,366,210 1/1968 Webster l192/113 B 3,366,211 1/1968 May 192/113 B Primary Examiner-Manuel A.Antonakas Attorney-Teagno & Toddy [57] v I ABSTRACT Limited slipdifferential which is selectively engageable and includes an improvedlubrication system. The limited slip mechanism uses a spring loadedfriction disk clutch pack which can break away at excessive torquelevels and prevent axle shaft breakage. The novel lubrication systemprovides improved lubrication of the clutch pack under all operatingconditions and prolongs the life of the clutch pack.

2 Claims, 2 Drawing Figures Weinrich 192/113 B X Pmmmm 3,762,503

' v sum UN 2 Big-i VENTORS LUBRICATION SYSTEM FOR LIMITED SLIPDIFFERENTIAL This application is a continuation of Ser. No. 841,088filed July 11, 1969 now abandoned.

This invention relates to a limited slip differential particularlyadapted for use in a vehicle interaxle, to positively transmit torque toeach of the driving wheels of the vehicle, such as a truck. Moreparticularly this invention relates to a selectively engageable limitedslip differential, using a preloaded friction disk clutch pack andincorporating an improved lubrication system for lubricating thebearings and more importantly the clutch pack for increased life.

The advantage of a limited slip differential is that improved vehicletraction is provided by its use. Thus, if one wheel of the vehicle is ona slippery surface and the other on a dry surface, the one wheel willnot spin out as in a normal differential. Instead, a limited slipdifferential will transfer torque to the other wheel and the vehiclewill be able to move.

Spring loaded clutch packs have been used in'the past to provide limitedslip differential action. The spring loading provides a safety featurethat lets the clutch pack break away and prevents excess stress on theaxle shaft.

Application Ser. No. 626,216 filed Mar. 27, l967 now US. Pat. No.3,448,635 to which reference is made, discloses a spring loaded frictionclutch limited slip differential that is an improvement over the priorart in that it is engageable as needed. In the prior art, the unit wasconstantly engaged. This produced extremely high wear on the clutchplates which scrubbed against each other to at least some degree duringthe entire time the vehicle was running. In the said U.S. Pat. No.3,448,635 a lubrication system is disclosed which provides lubricant tothe clutch pack as well as to the bearings and the gears of thedifferential.

The present invention provides an improvement to the lubrication systemof U.S. Pat. No. 3,448,635 and produces more positive lubrication to theclutch pack.

Accordingly, it is an important object of this invention to provide animproved lubrication system for a limited slip differential using aspring loaded clutch pack.

FIG. 1 is a sectional view of a differential mechanism as described inapplication Ser. No. 626,216 now U.S. Pat. No. 3,448,635; and

FIG. 2 is a sectional view similar to FIG. 1 but show-' ing the improvedlubrication system of the present invention.

Tl-IE PRIOR ART As shown in FIG. 1, the limited slip differential 10 isenclosed within a housing 14. A differential carrier 12 is fastened tohousing 14 by means of a flange l6'and bolts 18. In the differentialcarrier 12 is an opening 20 that receives a bearing assembly 22,consisting of two roller bearings 26, each including an outer race 24and an inner race and rollers 28. The two inner race and rollers 28rotatably support the input pinion gear 30 which is connected by adapterflange 32 to a drive shaft not shown. I

A ring gear 34 meshes with input pinion gear 30 and is connected to androtatably supported on a cup-shape differential case 47 by bolts 38. Thebolts 38 also hold a differential case cover 36 in place. Thedifferential case cover 36 has an axially extending hub 40 which isrotatably supported in the differential carrier 12 by a roller bearing42. The right hand side of differential case 47 is supported in abearing 146. The differential case 47 and ring gear 34 together define achamber 44 which receives a differential mechanism.

The differential case 47 comprises two halves 48 and 50. The half 48includes a flange 52 to which the ring gear 34 is fastened. Differentialside gears 54 and 56 are splined on axle shafts 58 and 60 and mesh withpinion gears 62. Pinion gears 62 are rotatably mounted on differentialpinon gear shafts 64, the ends ofwhich are fastened to differential case47 for rotation therewith. The two halves 48 and 50 of the differentialcase 47 are held together by bolts 66 through holes 68 of half 50 andinto threaded holes in the half 48.

The friction clutch pack 70 is positioned within the chamber 44.Friction disks 72 are spline connected at the outside diameter insuitable manner to the left half 48. Friction disks 72 thus rotate withthe ring gear 34. Between alternate friction disks 72 are interposedfriction disks 74 which are splined on their inside diameters to anannular, intermediate gear 88. The friction disks-74 thus rotate withthe annular intermediate gear 88. Disks 72 and 74 are loaded together bycompression springs 102.

Hub of the side gear 54 extends into chamber 44 and has teeth 82.Selectively actuatable clutch includes a sliding annular clutch member86. Teeth 87 thereon are adapted to engage teeth 82 of the side gear 54.Also, intermediate annular gear or friction plate driver 88 has teeth90, which engage teeth 89 of the sliding clutch member 86. When thesliding clutch member 86 is moved to the right in FIG. 1, teeth 87 and82 engage.

In the left hand position (dotted) of FIG. 1, the teeth 87 and 82 aredisengaged, although there is some overlap of teeth 89 and 90 so thatthe annular gear 88 and clutch sleeve 86 remain engaged.

As the sliding clutch member 86 is moved to the right, the followingaction takes place; I

The teeth 82 and 87 engage to provide a positive couple between ringgear 34 through the clutch pack 70, intermediate gear 88 and clutch gear86, to the side gear 54.

Thus the ring gear 34 and side gear 54 are locked together up to thepoint where the torque load on the axle shaft 58 will cause the clutchpack 70 to break away.

With the ring gear 34 and the side gear 54 locked together with piniongears 62 cannot turn. Thus there is no differential action and axleshafts 58 and 60 rotate at the same speed.

THE LUBRICATION SYSTEM The lower part of the axle banjo housingv forms alubricant reservoir 120, shown 90 out of position. Annular member 122held by bolts 66 to differential case half 50 moves through thereservoir to pick up lubricant. The lubricant which is picked up on theoutside surface of 122 is removed by a non-abrasive, pliable scraper 126mounted on the wall 128. A port 130 directs the lubricant from thescraper 126 to a flow chamber 132. A port 134 directs the lubricant tothe bearing assembly 22 which supports the input pinion gear 30. Aport.136 connects to passage 138 in hub 140 of the differential casehalf 50. This lubricates the bearing 146 and also directs lubricant intothe side gears 54 and 56 and pinion gears 62. As the gears 54, 56 and 62rotate, the lubricant moves through to chamber 148. From chamber 148 thelubricant flows through passages 150 to the outside of the clutch pack70. The lubricant exhausts from the clutch pack 70 generally along theoutside of the clutch member 86, back to the sump 120.

THE PROBLEM lt has been found in the design of FIG. 1 that centrifugalforce throws the lubricant to the outside of the clutch pack 70 and thusthe inside of the clutch pack does not receive adequate lubrication.Failures of the clutch pack have resulted.

The present invention provides improvements on the foregoing as follows:i

1. Novel lubrication directing system to get lubricant into the insideof the clutch pack as well as the outside root diameter of gear 88, andthus provide improved lubrication during all conditions of operation;

2. A novel lubricant pick up and scraper arrangement of improvedstructure; and

3. A novel lubrication exhaust.

As shown in FIG. 2, axially oriented ports 152 are formed in the lefthalf 48 of the differential case 47. The ports 152 lead from chamber 148to the inside diameter of the clutch pack 70 as well as to the outsideroot diameter of gear 88. These passages 152 discharge directly onto theannular intermediate gear 88 and between each of the friction disks 72and 74. This is made possible by opening the clearance between theinside of disks 74 and the outside root diameter of gear 88 to greaterthan specification. As the friction disks 72 and 74 rotate, theircentrifugal force moves the lubricant from the inside out. This causesthe lubricant to move radially outwardly along the abutting faces of thefriction disks and out to the periphery. The friction disks are thusbathed in lubricant over their entire surfaces.

Additionally, the lubricant from the ports 152 moves along the insidediameter of the intermediate annular gear 88 to lubricate the teeth 90and also the teeth 89 of the sliding clutch member 86.

The lubricant exhausts from the chamber 44 through radial ports 154formed in the outer periphery of cupshaped differential case 36. Thesize of ports 154 is such that lubricant feeds in through ports 152faster than it exhausts through ports 154. Thus, amplelubricant is alsodirected to bearing 42 and the annular clutch member 86.

THE IMPROVED PICK UP AND SCRAPER ARRANGEMENT In this improved invention,the differential case half 50 is formed with a cylindrical surface 156.The scraper 158 of non-abrasive pliable material is fastened to wall 128and extends out a sufficient distance to provide a wiping contact withthe cylindrical surface 156. This arrangement provides an improved flowof lubricant to the chamber 132 because the scraper 158 completely spansthe mouth of the outlet passage 130. This actually provides a push tothe lubricant as it travels through port 130 into chamber 132.

From the foregoing it will be evident that advantage is taken of thecentrifugal forces generated within the clutch pack 70 itself to provideits own lubrication power.

We claim:

1. A lubrication system for a selectively engageable limited slipdifferential drive mechanism comprising:

a housing having therein torque transmitting means including power inputmeans drivingly connected to a differential case, said differential casecontaining a differential drive mechanism having at least two drivenoutput gears, differential case cover secured to the exterior of saiddifferential case and forming a clutch housing with said differentialcase, rotatable friction clutch assembly mounted within said clutchhousing, said friction clutch assembly comprising;

a friction clutch pack having at least one first friction clutch membersecured to the inner walls of said clutch housing for rotation therewithand extending radially inwardly therefrom and at least one secondfriction clutch member fixed to a plurality of axially disposedcircumferentially spaced external splines on an intermediate gear, saidintermediate gear being internally splined for selective engagement witone of said driven output gears, the spaces between said intermediategear external splines and said second friction clutch member defining aplurality of axial fluid flow paths therebetween, said axial fluid flowpaths having an inlet end, an outlet end leading to a member to belubricated and a plurality of radial outlets leading to said first andsecond friction clutch members, and means for resiliently biasing saidfirst and second friction clutch members into frictional contact,

a slidable clutch member operable between engaged anddisengagedpositions for selectively engaging said intermediate gear andsaid one of said driven output gears, said clutch means in the engagedposition frictionally drivingly connecting said power input means andsaid one output gear,

said differential housing including a lubricant reservoir,

lubricant pick-up means movable through said reservoir to pick uplubricant and transport the lubricant from said reservoir,

lubricant directing means engageable with said pickup means for removinglubricant from said pick-up means,

passage means associated with said pick-up means and extending into saidclutch housing for moving lubricant into said inlet ends of said axialfluid flow paths for lubrication of said clutch pack radially outwardlythrough said friction members by the centrifugal force of the rotatingclutch assembly, and

exhaust port means through said clutch housing interposed said clutchpack and said lubricant reservoir, said exhaust port means of smallertransverse area than said axial fluid flow paths providing a restrictionto lubricant flow through said first and second friction clutch membersthereby assuring a portion of the lubricant in said axial fluid flowpaths said first and second friction clutch members to the member to belubricated.

2. The invention according to claim 1 wherein said passage meansassociated with said directing means leads into the central portion ofsaid clutch housing, exhausting into contact with said intermediate gearand the inside diameter of said friction clutch pack, and the clearancebetween the inside of the second friction clutch member and the outersurface of said intermediate gear being sufficient to pass the requiredsupply of lubricant.

1. A lubrication system for a selectively engageable limited slipdifferential drive mechanism comprising: a housing having therein torquetransmitting means including power input means drivingly connected to adifferential case, said differential case containing a differentialdrive mechanism having at least two driven output gears, a differentialcase cover secured to the exterior of said differential case and forminga clutch housing with said differential case, a rotatable frictionclutch assembly mounted within said clutch housing, said friction clutchassembly comprising; a friction clutch pack having at least one firstfriction clutch member secured to the inner walls of said clutch housingfor rotation therewith and extending radially inwardly therefrom and atleast one second friction clutch member fixed to a plurality of axiallydisposed circumferentially spaced external splines on an intermediategear, said intermediate gear being internally splined for selectiveengagement wit one of said driveN output gears, the spaces between saidintermediate gear external splines and said second friction clutchmember defining a plurality of axial fluid flow paths therebetween, saidaxial fluid flow paths having an inlet end, an outlet end leading to amember to be lubricated and a plurality of radial outlets leading tosaid first and second friction clutch members, and means for resilientlybiasing said first and second friction clutch members into frictionalcontact, a slidable clutch member operable between engaged anddisengaged positions for selectively engaging said intermediate gear andsaid one of said driven output gears, said clutch means in the engagedposition frictionally drivingly connecting said power input means andsaid one output gear, said differential housing including a lubricantreservoir, lubricant pick-up means movable through said reservoir topick up lubricant and transport the lubricant from said reservoir,lubricant directing means engageable with said pick-up means forremoving lubricant from said pick-up means, passage means associatedwith said pick-up means and extending into said clutch housing formoving lubricant into said inlet ends of said axial fluid flow paths forlubrication of said clutch pack radially outwardly through said frictionmembers by the centrifugal force of the rotating clutch assembly, andexhaust port means through said clutch housing interposed said clutchpack and said lubricant reservoir, said exhaust port means of smallertransverse area than said axial fluid flow paths providing a restrictionto lubricant flow through said first and second friction clutch membersthereby assuring a portion of the lubricant in said axial fluid flowpaths said first and second friction clutch members to the member to belubricated.
 2. The invention according to claim 1 wherein said passagemeans associated with said directing means leads into the centralportion of said clutch housing, exhausting into contact with saidintermediate gear and the inside diameter of said friction clutch pack,and the clearance between the inside of the second friction clutchmember and the outer surface of said intermediate gear being sufficientto pass the required supply of lubricant.